David Moyes is coming under increasing scrutiny from the Manchester United hierarchy with Sunday's 3-0 humiliation by Liverpool viewed as particularly disappointing due to the manner of the defeat.

While the position from the club's owners, the Glazer family, is that Moyes retains their support, United's Champions League last-16 meeting with Olympiakos on Wednesday evening has become vital to the manager's long-term job prospects.

With United trailing 2-0 from the first leg following an equally insipid display in Athens three weeks ago, particular attention is to be paid to how Moyes's players respond to him, and if he retains the vocal support within Old Trafford again enjoyed during the reverse to Liverpool.

After Olympiakos, United travel to West Ham United on Saturday before Tuesday evening's derby with Manchester City at Old Trafford, three games in which Moyes needs positive results.

While there is no particular will to sack Moyes, the United executive are becoming increasingly alarmed at the dismal displays and how far the team has fallen under Moyes since he replaced Sir Alex Ferguson last summer.

United are 12 points from a Champions League place, with only nine games remaining, and 18 behind the leaders Chelsea in what has become an increasingly dismal title defence.

Chris Smalling, meanwhile, missed Manchester United's training session on Tuesday morning, with the defender thought to be facing a prolonged absence because of a hamstring injury. Although Nemanja Vidic is available to play against Olympiakos, the captain is suspended for the trip to West Ham United and the derby at Old Trafford. So with Jonny Evans still out with a calf problem, Moyes may have to recall Rio Ferdinand at the weekend to play alongside Phil Jones.

During the training session at the club's Carrington complex on Tuesday morning United's squad appeared in high spirits, 48 hours after Sunday's 3-0 defeat to Liverpool at Old Trafford. Moyes took an active part in the session, working closely with a group that included Ryan Giggs, Wayne Rooney and Rio Ferdinand.